I'm not sure it's clear-cut. デジタル大辞泉 says that 景色 shares the same origin as 気色, so I can't help but wonder if it's just a borrowing, since 気色 is a clear usage of the kunyomi for け and しき, but け is not a typical reading for 景.
Ah, I meant "a clear usage of the readings", since け is an onyomi.
景 as け here seems to be ateji, according to multiple dictionaries it's derived from 気色 (as stated previously). Doesn't seem clear but probably not a standard reading but also not notable enough to be marked in dictionaries
「気」の代わりに、「景」を使うって当て字なの？もしかして、略した音読みの「けい」じゃないですか？だって、そういうのがあるある。例えば、「時計」とは、「ときけい」ではなく、「とけい」だけど、「時」使うからといって当て字というわけではないよね。
The reading of 時計 is also ateji, according to Wiktionary's etymology section.
https://en.wiktionary.org/wiki/%E6%99%82%E8%A8%88
時計 is tagged ateji as well in some kokugos and I also added that tag to JMdict.
E.g. 明鏡国語辞典 or 岩波国語辞典: 【《時計》】
I suspect it's very nitpicky to call 景色 a case of ateji, although wiktionary does so. Which may just be about formality. The fact that 景 cannot be read け still stands, and that may ultimately lead to the weird furigana.
In any case, jisho's furigana alignment system isn't perfect, so even if this isn't meant to be ateji in the system, it may still have some form of issue.
Misplaced Furigana?
The furigana is formatted as if it were a jukujikun which afaik is not the case, is this an error in a database jisho takes its info on or an issue on jisho's side?